Synthesis, Antioxidant Activity, and Determination of Binding Parameters of Meso-Tetra-4-Actophenyl-Porphyrin and its Palladium (II) Complex with Superoxide Anion Radicals

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Author(s): Amira Boutarfaia, Lazhar Bechki, Touhami Lanez*, Elhafnaoui Lanez, Mohamed Kadri.

Journal Name: Current Bioactive Compounds

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Abstract:

Meso-tetra-4-actophenyl-porphyrin (TAcPPH2) was synthesized by reacting 4-acetylbenzaldehyde with pyrrole in propionic acid, and used as a ligand for the synthesis of palladium (II) complex (PdTAcPP). The structure of the ligand and the complex were characterized by NMR and electronic spectroscopy. The antioxidant activity and the binding parameters of both the ligand and its complex with superoxide anion radical . (O2- ) were measured using cyclic voltammetry based assay. The assays were based on the measurement of the anodic peak current density of . O2- electrochemically generated by reduction of molecular oxygen in DMF. The complex PdTAcPP showed the highest antioxidant activity (0.73 ± 0.01 mg/mL) which is four times higher than that of the standard antioxidant α- tocopherol (3.04 ± 0.03 mg/mL). Binding parameters like binding constants, the ratio of binding constants and binding free energies were also measured. The value of the binding free energy ranging from -7.89 kJmol-1 for TAcPPH2 to -17.59 kJ.mol-1for PdTAcPP suggests an electrostatic interaction of . O2! with TAcPPH2 and PdTAcPP which has been found to be the dominant interaction mode. The kinetics of the interaction reaction of the ligand and complex was quantified having second-order rate constant values equal to 0.2 and 1.3 M-1 s-1, respectively.

Keywords: Porphyrin, Homogeneous rate constant, Cyclic voltammetry, Superoxide anion radical, Binding parameters, Antioxidant activity coefficient

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(E-pub Ahead of Print)
DOI: 10.2174/1573407215666191017105239
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